Eita Hoshizora is an 18-year-old who has just started university. He has been a gifted singer since childhood, but an incident in his past left him unable to sing in front of other people. When his twin sister Karina, a top idol, asks him to take the stage in her place, he cannot refuse her selfish request. He performs disguised as her, but the stunt upsets her sponsors and puts her place in the entertainment industry at risk. Eita then struggles to win back her standing as a top idol. The film is a Japanese theatrical recap of the Chinese donghua Jintian Kaishi Zuo Mingxing, told as a coming-of-age comedy about a brother and sister who trade places in the idol world.